This invention is generally directed to imaging members and processes for the preparation thereof. More specifically, the present invention relates to layered photoconductive imaging members with excellent mechanical characteristics, and wherein undesirable curling of the the supporting substrates are avoided or minimized when, for example, the member is formed as a flexible belt. In addition to belts, strong light weight drums may also be formed. In embodiments, the present invention is directed to the preparation of supporting substrates for layered imaging members, which processes comprise the polymerization of macrocyclic oligomers to provide polycarbonate substrates where curling is minimized without the need for an anticurling layer as presently needed in many situations for layered imaging members. Curling of the substrate can result in adversely effecting the life of the imaging member, and can cause images of poor resolution. Curling is primarily caused by the mismatch of thermal expansion coefficients between the polyester substrates, such as MYLAR.RTM., with the resin polycarbonate binder of the charge transport layer. This can be substantially overcome by coating an anticurl-back-coating layer of polycarbonate onto the side of the polyester layer opposite the charge transport layer. The present invention avoids the need for the second coating by producing a substrate of polycarbonate which will possess a similar thermal expansion characteristic to the polycarbonate of the charge transport layer. By avoiding the need for the anticurl coating, there is avoided the need for an additional manufacturing step, and substantially no emissions of volatile organic compounds associated with the coating step. In addition, intrinsic internal stresses can also be created in the transport layer as a result of its inability to relax completely on drying when coated onto a polyester film. These stresses will influence the life of the photoreceptor and its failure modes, and this can be minimized when the supporting substrate is also a polycarbonate. These and other disadvantages can be avoided or minimized with the processes of the present invention. Also, in embodiments the present invention is directed to the fabrication of supporting substrates by the in situ polymerization of macrocyclic oligomers. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the charge transport layer and the substrate, or positively charged when the charge transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of the appropriate charge. Generally, the imaging members are sensitive in the wavelength regions of from about 400 to about 850 nanometers, thus diode lasers can be selected as the light sources in some instances.
Layered imaging members with supporting substrates, such as aluminum, and polymeric materials, photogenerating and charge transport layers, including charge transport layers comprised of aryl diamines dispersed in polycarbonates, like MAKROLON.RTM., are known, reference for example U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference. More specifically, in U.S. Pat. No. 4,265,900 there is illustrated an imaging member comprised of a supporting substrate, like aluminum or MYLAR.RTM., which have a tendency to curl, a photogenerating layer, and an aryl amine hole transport layer comprised of amine molecules dispersed in a polycarbonate. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
Similar photoresponsive imaging members with squaraine photogenerating pigments are also known, reference U.S. Pat. No. 4,415,639. In this patent there is illustrated a photoresponsive imaging member with a substrate, a hole blocking layer, an optional adhesive interface layer, an organic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and a hole transport layer. As photoconductive compositions for the aforementioned member, there can be selected various squaraine pigments, including hydroxy squaraine compositions. Moreover, there is disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions.
The use of selected perylene pigments as photoconductive substances is also known. There is thus described in Hoechst European Patent Publication 0040402, DE3019326, filed May 21, 1980, the use of N,N'-disubstituted perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive substances and wherein the supporting substrate can be a metal like aluminum, or certain polymeric materials. Specifically, there is, for example, disclosed in this publication N,N'-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyldiimide dual layered negatively charged photoreceptors with improved spectral response in the wavelength region of 400 to 700 nanometers. A similar disclosure is revealed in Ernst Gunther Schlosser, Journal of Applied Photographic Engineering, Vol. 4, No. 3, page 118 (1978). There are also disclosed in U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance with the teachings of this patent, the photoconductive layer is preferably formed by vapor depositing the dyestuff in a vacuum. Also, there is specifically disclosed in this patent dual layer photoreceptors with perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have spectral response in the wavelength region of from 400 to 600 nanometers. Also, in U.S. Pat. No. 4,555,463, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a chloroindium phthalocyanine photogenerating layer. In U.S. Pat. No. 4,587,189, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a perylene pigment photogenerating component. Both of the aforementioned patents disclose an aryl amine component as a hole transport layer.
In copending application U.S. Ser. No. 537,714, the disclosure of which is totally incorporated herein by reference, there are illustrated photoresponsive imaging members with photogenerating titanyl phthalocyanine layers prepared by vacuum deposition. It is indicated in this copending application that the imaging members comprised of the vacuum deposited titanyl phthalocyanines on supporting substrates such as certain polymeric materials and aryl amine hole transporting compounds exhibit superior xerographic performance as low dark decay characteristics result and higher photosensitivity is generated, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example U.S. Pat. No. 4,429,029 mentioned hereinbefore.
In copending patent application U.S. Ser. No. 905,697 the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of photoconductive imaging members which comprises coating a supporting substrate with a photogenerator layer comprised of photogenerating pigments, and subsequently applying to the photogenerating layer a mixture comprised of charge transport molecules and cyclic oligomers, and wherein said mixture is heated to obtain a polycarbonate resin binder from said cyclic oligomers.
The disclosures of all of the aforementioned publications, laid open applications, copending applications and patents are totally incorporated herein by reference.